WMS:Time Computation Arcs

The Node → Flow arcs command in the Feature Objects menu allows you to automatically develop time computation arcs by tracing the flow path across a TIN or DEM and saving an arc representing the path so that an equation can be assigned to it. You can investigate where the arc(s) will be created using the flow path tool and selecting points on the TIN or DEM since the same functions for flow are used to create the arcs. The process requires the following three steps:

1. Create a feature points at locations where the flow path segments should begin.

2. Make sure any feature points you wish to use to create time computation arcs are selected.

3. Choose the Node→Flow arcs command.

You will be asked if you want to create one continuous arc or multiple arcs. If you respond with one continuous arc it will create an arc representing the flow path from the selected feature point to the next downstream outlet. If you choose to create multiple arcs it will break the arc into separate arcs if the flow path encounters a stream.

Flow Paths to Time Computation Arcs

When using the Node → Flow Arcs command in the Feature Objects menu, only the portions of the stream that are part of the flow path from the selected point to the outlet get converted to time computation arcs. If you wish to compute the lag time between consecutive outlet points then you will need to convert the remaining stream portions to time computation arcs. This is the purpose of the Streams → Flow Arcs command. Not all streams are converted when using this command, only those stream segments that connect outlets. This command works for either TIN or DEM feature object stream segments.

Related Topics

• Stream Travel Computation Arcs
• Time Computation Coverage
• Calculating Travel Times